For the purposes of the present invention, end mills can be theoretically divided into two general groups, namely insert-mills and solid end mills.
Insert-mills are milling tools which comprise tool holders with pockets and replaceable inserts, typically indexable, configured to be mounted in the pockets. An advantage of insert-mills is that the replaceable inserts, which are made of comparatively expensive, harder, material constitutes a relatively small portion of the milling tool. The tool holders comprise a shank which is held securely by a collet or chuck during milling.
Unlike insert-mills which regularly require replacement of small inserts and less regularly require replacement of the tool holder, solid end mills comprise integrally formed teeth and the entire solid end mill is replaced after it is worn. Solid end mills also comprise an integrally formed shank which is held securely by a collet or chuck during milling. Accordingly, solid end mills utilize far more comparatively expensive material than insert-mills. Despite the comparatively higher cost, one of the advantages of solid end mills over insert-mills is that the solid end mill's single integrally formed body can be manufactured with a comparatively smaller diameter (typically less than 20 mm diameter, with smaller diameters being more popular, e.g., at about 12 mm diameter) allowing milling in relatively smaller locations than is possible or practical with insert-mills.
While very small inserts are known, solid end mills are still commonly preferred at the relatively smaller diameters for a variety of reasons.
Accordingly, the present invention is directed to inserts and insert mills that have a range of design features that make them functionally and economically competitive with solid end mills at cutting diameters of 20 mm and less, particularly in the range of 9 to 16 mm, preferably 9 to 12 mm.
A publication of interest is EP 3050655, which discloses single-sided two-way indexable inserts for small diameter tool holders.